A8_Microfluidics_fundamentals_II
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Active micromixers - temporal pulsing
Planar flow channels may be used to induce chaotic advection but require temporal control of the flow field.
The introduction of each fluid was staggered so that they occupy the entire channel, resulting in the two fluids being layered axially along the length of the channel.
→ creates an axial concentration gradient so that axial diffusion tends to mix the two streams (helped by the parabolic profile of the pressure driven flow)
An integrated bioanalytic device
Tissue organization, culture and analysis in microsystems: cell chips
Jensen et al, Nature 442, 403 (2006)
Difficulty: integration of fluidic, optical, electronic and biological components
•Advanced tissue organization and culture can be performed in microsystems by integrating homogeneous and heterogeneous cell ensembles, 3D scaffolds to guide cell growth, and microfluidic systems for transport of nutrients and other soluble factors in precisely defined spatial and temporal patterns using integrated microfluidic systems.
•Microsystems technology can also fractionate heterogeneous cell populations into homogeneous populations, including single-cell selection, so different cell types can be analysed separately.
•Microsystems can incorporate numerous techniques for the analysis of the biochemical reactions in cells, including image-based analysis and techniques for gene and protein analysis of cell lysates.
Microreactor technology for chemical production
•high heat and mass transfer rates allow reactions under more aggressive conditions and higher yields
•new reaction pathways not possible in conventional equipment
•distributed point-of-use synthesis with production scale multiple microreactors of highly reactive and toxic intermediates
•scale-up to production levels by replication of microreactor units eliminates redesign and pilot plants
•scheduled, gradual investment in new chemical production facilities, reducing risks and capital costs
a new paradigm?
Cytos microreactor (three-step synthesis of pigments): 6 microreactor chips working 24 hours/day produce 30 tonnes of pigment a year
Efficient heat transfer
5 m3 reactor stirred at 500 rpm
Efficient mixing
Integrated microreactor in a circuit board
•Functionality
–small thermal inertia, high gradients of physical properties, uniform temperature, short residence time, high surface-volume ratio
•Safety
–suppression of flames and explosions, no large-scale hazards
•Cost
–rapid screening and high throughput, small volume of required reagents, easy numbering-up (particulary advantageous for fine chemicals and pharmaceutics)
•Scientific merit
–Laminar regime of fluid flow, easily handled by most computational fluid dynamics tools
Microreactor for microfluidic synthesis and surface engineering of colloidal nanoparticles
Langmuir 20, 8604 (2004)
Microreactors for fuel processing
Klavs Jensen, MIT
Rapid discovery and optimization of catalytic processes
pressure drop in pressure drop channels much higher than in reactor equalizes flow distribution